be increased to a certain degree, as in giving opium in
nervous fevers, the arterial contractions may be performed more frequently
than natural, yet with less strength.

And thirdly, if the sensorial power continues the same in respect to
quantity, and the stimulus be somewhat diminished, as in going into a
darkish room, or into a coldish bath, suppose of about eighty degrees of
heat, as Buxton-bath, a temporary weakness of the affected fibres is
induced, till an accumulation of sensorial power gradually succeeds, and
counterbalances the deficiency of stimulus, and then the bath ceases to
feel cold, and the room ceases to appear dark; because the fibres of the
subcutaneous vessels, or of the organs of sense, act with their usual
energy.

A set of muscular fibres may thus be stimulated into violent exertion, that
is, they may act frequently, and with their whole sensorial power, but may
nevertheless not act strongly; because the quantity of their sensorial
power was originally small, or was previously exhausted. Hence a stimulus
may be great, and the irritation in consequence act with its full force, as
in the hot paroxysms of nervous fever; but if the sensorial power, termed
irritation, be small in quantity, the force of the fibrous contractions,
and the times of their continuance in their contracted state, will be
proportionally small.

In the same manner in the hot paroxysm of putrid fevers, which are shewn in
Sect. XXXIII. to be inflammatory fevers with arterial debility, the
sensorial power termed sensation is exerted with great activity, yet the
fibrous contractions, which produce the circulation of the blood, are
performed without strength, because the quantity of sensorial power then
residing in that part of the system is small.

Thus in irritative fever with arterial strength, that is, with excess of
spirit of animation, the quantity of exertion during the hot part of the
paroxysm is to be estimated from the quantity of stimulus, and the quantity
of sensorial power. While in sensitive (or inflammatory) fever with
arterial strength, that is, with excess of spirit of animation, the violent
and forcible actions of the vascular system during the hot part of the
paroxysm are induced by the exertions of two sensorial powers, which are
excited by two kinds of stimulus. These are the sensorial power of
irritation excited by the stimulus of bodies external to the moving fibres,
and the sensorial power of sensation exc